1) Field Of The Invention
The invention relates to jointing compounds with improved resilience based on aqueous dispersions or on water-redispersible powders of vinyl ester-ethylene copolymers or acrylate polymers.
2) Background Art
Jointing compounds having dispersions as binders are used in sectors where they are not subjected to prolonged exposure to water. They serve to connect adjacent materials, including those of different types, and in this manner to prevent penetration of harmful substances, such as gases and liquids, in particular water, into the "joint". This prevents damage to the building materials underneath, for example by moisture penetration or frost, which would impair the effectiveness and the permanence of building materials. Besides this, esthetic reasons make it desirable to use jointing compounds for permanent closure of joints.
Jointing compounds having dispersions as binders are predominantly used in connecting joints and expansion joints since, in contrast to jointing compounds based on silicones, they can be counted as relatively plastic systems. It is vital for the permanence of the joint structure that the adhesion to the side of the joint is sufficiently high. The binders are also required to have high resistance to water and weathering when used outdoors.
The binders in jointing compounds having dispersions as binders are vinyl acetate-ethylene copolymers or homo- and copolymers of acrylates. EP-A 303701 discloses joint fillers which are formulated from vinyl acetate-ethylene copolymer, CaSO.sub.4 hemihydrate, hollow silicate microspheres and cellulose fibers. EP-A 339427 (U.S. Pat. No. 5,004,769) describes jointing compounds and coating compounds based on aqueous dispersions of acrylate polymers and nonionic cellulose ethers. EP-A 423613 (U.S. Pat. No. 5,118,730) relates to a specific procedure for preparing jointing compounds based on aqueous polymer dispersions and nonionic cellulose ethers, the nonionic cellulose ethers being slurried in small amounts of water before they are added.
An important property for the permanence of jointing compounds, for example outdoors with components which expand and contract as a result of weather conditions, is the ability to absorb stresses resulting from changes in joint width. For this, a requirement is sufficient elasticity, besides good adhesion. In addition, the jointing compound should be able to regain its initial dimensions when joint width reduces, i.e. it should have good resilience. The jointing compounds having dispersions as binders known hitherto and based on acrylate polymers or on vinyl acetate-ethylene copolymers have unsatisfactory resilience, since their Theological behavior is to deform in a manner which is to some extent plastic.
The object was therefore to provide jointing compounds which are based on vinyl ester-ethylene copolymers or on acrylate polymers and which, besides good adhesion and elasticity, are in particular distinguished by high resilience.